Many activities concerned with lens metabolism are controlled by inhibitory proteins. We have demonstrated that proteins are present in crude lens extracts which inhibit the enzymes ribonuclease, deoxyribonuclease and trypsin. The purpose of this research will be to purify these inhibitory proteins and to determine their properties. The levels of these inhibitors will be studied in the various regions of the lens and in experimental and senile cataracts. Previous evidence suggests that these inhibitors are induced during lens cell differentiation and are inactivated during cataractogenesis. We further intend to measure the inactivation of these inhibitors by extracts of cataractous lenses and to correlate these data with the loss of activity induced by specific reagents which interact with the purified proteins and destroy their biological activity. With these systems we will be able to test specific protective reagents for their ability to prevent or reverse the inactivation of these inhibitor proteins.